GIMP Version: 2.8.14
Operating System: Windows
GIMP Experience: Basic Level

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Hi,

I have a series of images that were taken using a standard colour reference card. I need to adjust each image so they are as similar as possible.

I have already adjusted the white balance using the neutral grey and white squares on the colour card, but this only partly removed the differences among images.

Ideally I'd like to use an objective method since the composite image being created is for a scientific research publication.

Any ideas how I can go about doing this?

Thanks,
Dean

As a starting point use the whitebalance script by Luca de Alfaro. Basically you use the color picker to set the foreground to the current color of anything in the image that should have been neutral gray (in your images, a gray square in the chart), and use the "Make foreground gray" function.

The script can be likely hacked to force the gray value to some specific RGB value to make sure that the exposure in the same but there seem to be a lot of variability in the exposure curve and you may have to use the two gray squares.

Asking on pixls.us may point you to more powerful/specialized photo applications (*).

(*) this said, posting pictures of dead penguins in a forum where many people use Linux is a bit bold

My software skills are basic - I am completely out of my depth with script! Indeed even reading the word makes me cringe, so I'm confident I won't be able to 'hack it' to force it to work off a non-neutral RGB colour.

I already ran the whitebalance using the grey square. That standardised the colour tones across the images, but I'm left with differences in saturation/brightness (e.g. some of the blue squares are considerably paler than others and some red squares are comparatively dull). I could adjust each image manually, but I fear that is introducing too much subjectivity (that is, I want a computer to do it!).

PS they aren't penguins, but a different type of seabird (petrel) that can fly.